1) Lightly oil eggplant and prick all over with a fork. Grill or bake in oven until soft, about 20 minutes. Let cool. Then remove peel and chop the flesh. Set aside.
2) While that's going on, sauté onion and black mustard in olive oil. Add other spices and sauté until fragrant. Mix in remaining ingredients. Simmer gently until the eggplant is tender and done, about 15 min. You may need to add a little water to keep the tomato from sticking. Serve over rice, quinoa or millet.
This dish tastes better if you make it ahead of time and reheat it.
Source of recipe: This recipe was inspired by a friend's memories of a dish prepared by her Indian roommate in college.